The present invention relates to an electromechanical converting device which is used in an actuator, an ultrasonic motor, and the like of industrial robots and, more particularly, to the improvement of a laminated displacement device in which a plurality of thin plates made of an electromechanical converting material are laminated through internal electrodes, thereby assuring a predetermined displacement amount.
Hitherto, a laminated piezoelectric transducer which is used in a displacement device which is coupled to an output device such as a positioning mechanism of an X-Y stage, a brake, or the like uses a method whereby electrodes are provided for thin plates made of a piezoelectric ceramic material which are worked into a predetermined shape and are polarized and, thereafter, the thin plates are joined directly or through thin metal plates by an adhesive agent of the organic system. However, the laminated piezoelectric transducer which is constructed by laminating the thin plates by using the adhesive agent as mentioned above has drawbacks such that the adhesive agent layers absorb a displacement due to the vibration of the piezoelectric transducer in dependence on the use conditions, the adhesive agent deteriorates due to the environment of a high temperature or the use for a long time, and the like.
Therefore, in recent years, a laminated piezoelectric transducer of the laminated chip capacitor structure type has been put into practical use. That is, for instance, as shown in JP-B-59-32040, a paste-like piezoelectric ceramic material which is obtained by adding binders and solvents into raw material powder and kneading is formed like a thin plate having a predetermined thickness and a conductive material such as silver-palladium or the like is coated onto one or both surfaces of the thin plate, thereby forming an internal electrode. A predetermined number of such thin plates are laminated and adhered with a pressure and are, further, worked into a predetermined shape. After that, they are sintered to obtain ceramics. External electrodes are formed on both side surfaces of the laminate. The laminated piezoelectric transducer with the above construction has advantages such that an adhesive property of the joined portion between the thin plate made of the piezoelectric ceramic material and the internal electrode is excellent and the thermal characteristics are also stable, so that the laminated piezoelectric transducer can be sufficiently used even in an environment of a high temperature, a deterioration is extremely small for a long time, and the like.
What are called alternating electrode type and whole surface electrode type (for example, JP-A-58-196068) have been known as laminated piezoelectric transducers.